The transmission of pathogenic microorganisms by hands in medical practice has long been recognized as a source of infection in the treatment of patients and in surgery. Physical barriers such as surgical gloves often prove insufficient protection because of the high incidence of punctures and minor cuts by surgical instruments.
Following the usual scrub-up procedure, the application of antiseptic fluids to the hands of operating theatre staff prior to surgery is common practice to reduce viable organisms on the skin to a minimum.
It would therefore be a great advantage to combine washing and disinfectant action in one single operation. Most suitable for a combined head washing and degerming product would be an antibacterial agent which combines a broad antibacterial spectrum, covering the whole range of Gram positive and negative bacteria, with continuous residual bactericidal activity after application, and low irritation to the skin. Chlorhexidine has such properties and is available in water soluble forms such as the gluconate and acetate salts.
A disadvantage of the chlorhexidine antibacterial agents is that through their cationic character they are incompatible with anionic surfactants. Combination with cationic surfactants for hand washing is not advisable as the high concentration of the cationic surfactant necessary for good detergency could give rise to skin irritation. Amphoteric surfactants, due to their anionic and cationic character, depending upon pH are equally unsuitable for the reasons given above. It was further found that chlorhexidine in combination with nonionic surfactants suffers considerable losses in antibacterial activity.
Australian Patent 459,343 describes a skin cleansing composition containing salts of chlorhexidine in combination with a polyoxyethylene-polyoxypropylene block copolymer. The block copolymer is a low-foaming nonionic surfactant, and high proportions of as much as 20-25% of such copolymers are necessary to give sufficient sudsing expected from that type of product, even when foam boosters such as an alkyl amine oxide is incorporated in the composition.
The compositions exemplified in Australian Patent 459,343 contain 4% w/v chlorhexidine which is well above the amount which normally would be required for skin disinfection. This is due to the fact that at the high concentration of nonionic surfactant, considerable deactivation takes place leaving only a small amount of the chlorhexidine available for antibacterial activity.
It is well known that nonionic surfactants have an adverse effect on the skin, through defatting which increases with higher concentration especially on sensitive skin. High concentrations of chlorhexidine have an irritating effect on the skin. Reduction of the concentration of chlorhexidine and nonionic surfactants in a nonionic surfactant system, while still retaining sufficient available chlorhexidine for the desired antibacterial effectiveness, would not only effectively reduce the risk of skin irritation on repeated application, but also reduce costs of such compositions by a considerable degree.